Achillea millefolium L.

• Authority

  Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

• Family

  Asteraceae

• Scientific Name

  Achillea millefolium L.

• Description

  Species Description - Aromatic, rhizomatous perennial 2–10 dm, very sparsely to rather densely villous or woolly-villous; lvs pinnately dissected, the blade 3–15 cm, to 2.5 cm wide, the basal petiolate, all but the lowest cauline sessile; heads numerous in a flat or round-topped, short and broad, paniculate- corymbiform infl, the disk 2–4 mm wide; invol in ours 4–5 mm; rays ca 5, white or occasionally pink, 2–3 mm; disk-fls 10–30; x=9. Various habitats, but especially in disturbed sites, circumboreal, and throughout our range. June–Nov. A highly variable circumboreal polyploid complex, not yet satisfactorily sorted out into infraspecific taxa. Typical European A. millefolium, a hexaploid with flat lvs, the relatively broad ultimate segments all in nearly the same plane, is rarely intr. in our range. Our native forms are mostly tetraploid, with narrower lf-segments disposed in various planes so that the lf is airily 3-dimensional. These represent the transcontinental ssp. lanulosa (Nutt.) Piper, consisting of several vars. as yet not well understood. Another native tetraploid, called var. nigrescens E. Mey., extends into our range from the ne., reaching Mass. and n. Mich. It is a relatively small plant with flat lvs like typical millefolium, distinguished by the dark brown or nearly black margins of the invol bracts.

• Common Names

  common yarrow